Telephone transmitter



April 30, 1929. E, A GRAHAM E'r AL TELEPHONE TRNSMITTER 3y Sheets-Sheet Filed June l0, 1927 l l Invenon:

Pll 30, 1929. E.- A), GRAHAM ET AL ,TELEPHONE TRANSUIII TTER Fild Jung 1o, 1927 s sheets-sheet 2 April4 30, 1929.

E. A. GRAHAM E-r Al..

TELEPHONE TRANSMITTER Filed June lO, 1927 I5 Sheets-Sheet 3 Fate-rated ipr. Eil, T5329..

narran STATES Y" igiene PartnrA OFFICE.

EDWARD ALFRED GRAHAM, DECEASED, LATE OF CROFTON PARK, BROCKLEY, ENG- LAND, BY MARIA GRAHAIVI, EXECUTRXX, OF BECKENHAM, ENGLAND, .AND AL` FRED GBAHAIJI, EXECUTOR, OF FOREST HILL, ENGLAND, AND LESLIE HAROLD PADDLE, OF CRFTCN EARL. BROCKLEY, ENGLANLD, ASSIGNORS TO GRAHAM AMPLION LIMITE, OF LONDON, ENGLAND 4 TELEPHONE TRANSMITTER.

Application lcd .lune 10, 1927, Serial No. 197,979, and in Great Britain June 18, 1925.

invention relates to that type ot telephone transmitter in which a diaphragm, when influenced by soundwaves or other vibrations, is caused to vary the resistance ot' contact between a mass ot carbon granules situated between stationary electrodes, the arrangement being such that the sound waves or other vibrations impinge on the diaphragm in a direction substantially at right angles to the current-flow through carbon granules ldisposed between the electrodes and thereby cause an increase or decrease oi' contact re-v The object ot Athe present vinvention is to construct a microphone ot the type just mentioned thatshall be very sensitive to ineen ing sound waves and at the same time maintain the purity necessary in amplilied reproduction. lt will be 'followed that an advantageous consequence ot provid-ing a very sen.- Vsit-ive transmitter is that the number ot' stages oi' ainpliiication can be reduced, this resultin a decrease et the distortion which is consequent onthe number oit stages ot ampliiication generally used with such a` transmitter.

For this purpose, in a teleitihone transmitter according to the invention, two oir-more ationary electrodes are employed cach supported in such a manner in or on a block or bedv o'iinsulating material that current can flow Yfrom one to the other through a path ot granular carbon, or equivalent (hereinafter rei'erred to as carbon g les) which exists as a layer oi convenientv depth between thesaid electrodes. A diaphragm 'formed oi material 'such Ytor example as empire cloth, mica, -in sheet rubber, or other maite ial 'having siNiilar characteristics, is

.upper plates and material n f electrodes and other parts.`

plan an upper lclamping plate for the dia-q placed in such relationship to the carbon, granules that it forms a skin which touches the said carbon granules and is adapted either to be lirmly or lightly retained along a diametrical portion so that such rportion cannot readily vibrate, while other or lateral portions, touching the granules, can' freely be influenced by sound vibrations in order to vary the resista-nce between the contact siii'- aces of the carbon granules thro-ugh which a steady electric current 'from a'battery or other source ,otl electric supply is caused to 'flow in a direction parallel to the diaphragm, suoli varying resistance conforming. to the varying intensities and frequencies of the intluencingsound waves.

The lateral vihratory portions ofthe diaphragm may be adapted to have different natural periods of vibration. V

A telephone transmitter embodying the invention canv be variouslyt constructed.

ln the accompanying' illustrative drawings, Fig. l shows in vertical sectioinone construction of telephone transmitter embodying the present invention. Fig. 2 shows the same in plan with the cover and 'diaphragm removed. .Figs. 3 and l show respectively in vertical section and plan, a block -ot insulating material used in the transmitter. Figs. 5 and G show respectively in plan and cross section, one ot the two carbon electrodes used therein and Figs 7 and 8 are similar views to 5 and 6 of one of two distance pieces for use between the electrodes. Fig. 9 shows in plan, azbottom clamping ring and Fig. l() shows in plan, a cover plate having sound openings therein, Figs'll, 12, 1B, and lil are vertical sections showingA modiiied forms ot the transmitter, Fig'. l5 is a vertical section and Fig. 16 a plan showing another modiiication of `the transmitter. Fig. v17 shows in vertical section, a turther moditication, Fig. 18V showsthe same in plan with the 19 isa planet the insulating block with the Fig. 2O shows in phragm. Fig. 2l shows'the underside .oit a plate for retaining` the-carbon granules within the space between carbon electrodes, blocl;

and diaphragm.

diaphragm removed. Fig.

i by one such strip 11, the diametrical portion and 2, and having lits upper surface substantially in the same plane as the upper surfaces .of the latter electrodes, may be incorporated in the transmitter according t0 the requirements of the external circuit with which the transmitter is to be used.

According to the modification shown in Fig. 13, instead of holding a diametrical portion of the diaphragm between two strips of rigid and flexible insulating material (Fig. 1), or between two strips of rigid material (Fig. 11),y it is acted upon from the outside ofthe inner side of the diaphragm, opposite the strip being held against the carbon granules 14 by the outer strip 11 of flexible or rigid material. .l

Fig. 14 shows a modification,wherein the segmental electrodes 1 and 2 are formed with grooves 1n and 2, and the diaphragm 7 beais at its outer' portion on such electrodes and its diametrical portion is clamped between two stri is 1t) and -11 ofricid insulatinfl mafr terial, the lower of which is held in recesses in the annular wall of the block 3 of insulating material. Y

According to a further modification, shown in Figs. 15 and 16, the outer side ofthe diaphragm '7 may be wholly or partly covered with alayer 28 of material o f a stiffer or more rigid nature than that of which they diaphragm is formed and which has a large num'- ber of openings or perforations therein so that the outer surface of the diaphragm, or that portion thereof covered by the said layer of material, presents a large number of separate zones or areas to the external air. The said outer layer of comparatively lrigid material may be composed of wire gauze or net, or Y of textile fabric of an openworl: nature and be stiflened by the application thereto of a stiffening substance, as for instance, dope, or a f phenolic condensation product. Or it may be composed ofthin sheet material, as for ex-v ani'ple,`thin sheet metal, Celluloid, mica or the like, formed with a large number of apertures.

foratcd sheet material, may vary, but usually wil comparatively small, say for example, not exceeding an area of yabout one quarter inch square. The reticulated or-perforated layer of material. ori'nay vbe made of such stiffness that it will deaden'or minimize vi- Vbiations of the portion of the diaphragm against which it bears while leaving the portions ofthe diaphragm opposite the'open-` ings in the said material free to vibra-te under the action of external sound waves. The

layer28 of reticulated or perforated material may merely be arranged to bear or press against the diaphragm, or it may be attached to thediaphragm by a suitable adhesive.

In come cases, the inner surface vof'snch a sectionalized diaphragm, or a portion thereof,

The size of the mesh in recticulatedv material, or the size of the openings in pei-` of which is provided with short studs 30 and 31a of like material. The diaphragin7 is clamped at its peripheral portion between clamping plates 32 and 33 and bears upon the studs 30u and 31a, the two plates having large openings therein as shown in Figs. 18 and 20. The opening in the bottoni plate I32, which is of Ainsulating material, serves to confine the carbon granules 14 in place between the blocli` 3 and diaphragm 7 yand over the electrodes. The upper plate 33, may be of metal. cover plate formed with two oppositely arranged sound openings 12a and 12". To its underside is secured a diametrically arranged clamping strip. 11, preferably of soft material such as rubber, that bears against a dia.- metrical portion of the diaphragm 7 arranged at right angles to the diametrical line joining the central portions of the electrodes 1 and 2 and serves to depress thesaid portion of the diaphragm and hold it firmly against the adjacent mass of carbon granules 14. rl`lie said plate 12 is also preferably provided on its underside` with two diametrically arranged studs 35 and 36 that also bears against the diaphragm 7 and press thelatter against the carbon granules. rlhe plates 32, 88 and 12 are firmly secured together and to the block 3 by screws passing vthrough holes' 37 in these parts. 381s ak hole in the block. 3. through which the carbon granules 14 can be introduced, It is normally closed by a screw plug 39. 18 and 19 are terminals connected tothe electrodes 1 and 2. The openings 12il and 12h in the cover plate 12 may be protected by a layer 25 of perforated material clampedbetween the central portion of the said plate 12 and a disc 40 and between the peripheral por- Y tion of the said plate and a cap ring 21 fixed to a casing` 2Gas in Fig. 1. p

In each arrangementthe two portions of thediaphragm at oppoiste sides of the dianietrically held portion of the diaphragm is or may be stressed to dihereiit degrees so that Vthey shall have` different periodsof vibra' tions. Also,the peripheral portion of the diaphragm may, in some cases, beclamped 12 is a` between a peripheral portion-Of the insulating 1 block and an upper clamping ring, as in Figs.

14 and 15, insteadfofbetween two clamping rings fixed to the peripheral portion of the block. .y 1- f i The upper surfaces of the eiectrodes me", es shown in F 17, 18 :in d 19, be provided With e plurality of projections for instance, ot pyramidel shape, and provide a large aree ot conta-ct with the layer of granular conducting' material bearing against them.

1What We claim is l. A telephonie transmitter comp support ot insuietiz'ig` materiel, oppe f laterally arranged eiectrodes carried by seid support, a layer of granular eoinhictinfY met@- riel exieuding over the fece ot seid support and between seid electrodes through which and the layer conducting materiel an eiectric current can How, a, sound sensitive di :1L- phregm termed oit thin substentieliy nonrese/rigen; non-condnotingv meteri skin touching1 the layer et gri-entf id seid ou the and ineens adapted to h( eiong e. diainetricel port i such portion cannot vibrate freely whiie tions of the diziphregm #it mgposite such held portion are, luider the z sound wives oit varying intensi quency, impingiup; thereon, .culi

Vibration in Contact with seid leyerducting` unite-rial :ind thereby vary triczd resistance thereof Yfor the pureose set forth.

2. A telephone transmitter zic-ordine' te the preceding,l claim, characterized therebj.Y that the Vib 'utory portions of the diaphragm et opposite sides oi the diemetriczdiy heid portion and touching the layer ot grenuier materiel, have different naturel periods oit vib fation.

3. A telephone transmitter according claim l, wherein the vibrutory portions o't the dioiihragm at opposite sides of the cierietri-v caiiy held portion of the diaphragm ere stressed to dii/ferent degrees so that theb here (fiti'erent periods oi' Vibration,

A telephone transmitter accor-ling; cisti n l, Whe-r yin the d' uetriceitT hv tion ot.' the diuphinpjm is errer ged angles to the direction ot curie through the layer oit granular c materiel between the electrodes.

5. A telephone transmitter according' to claim 19 wherein the dieinetriceiiy heid portion of the diaphragm is heid against the layer ot nnuier conducting material, by e, strip et sett or yielding meter-iet.

(i. A teiephone transmitter according to claim l., wherein the diemetriceiy heid portion ot the diaphragm is held against the layer ot granular conducting materiel.

'i'. A. telephone trensniitter according to claim Livherein the support oit insulating; materiel is ot circuler shape und the peripheral portion et the diaphragm is secured to such support, the diemetriceiiy held portion of the diaphragm being arranged et right angles to :L tine between the electrodes.

8, A telephone transmitter according to ,ele

claim l9 wherein the ley/er of granular conducting materiel extends over the electrodes.

9, it telephone 'transmitter according to claim l, wherein e cover plete having sound inlet openings therein is secured over but spaced from the diaphragm.

l0. telephone tinnsinitter comprising e block ot' insnhitingl inuteriui7 oppositeiy und interfiiiy arranged electrodes carried thereby, layer ot granular conducting' ineteriei carried by seid block end arranged between eiectrodes, a diaphragm of thin substaniy non-resonant and nt n-conchictingY nie- 1 forming e skin touching the layer or conducting materie?. secured et its peripheryY te seid hiock, strip insite itil holding seid diep`negm along e dieinetr d portion thereof, errenged et right engi to a line joiningfij the electrodes, against seic ier materiel While portions o the di opposite sides oi seid heid portion are ezipebie oi vibration, under the acti n et ei;- ternel sound wei/es, 'n contact with said granular mete ini, and @coi/er plete secured over but spaced from sii-.id diaphragm and haring sound inlet. therein opposite the Vi-V the diaphragm, saidv cover .s the strip hoiding ineens i 7 a seid diaphragm dong e diemetr'cei portion efeoi, lrrenged et right angles to :i line the electrodes, if nnuier i While .1 ortions o seid heid por .i e sides et' e .sit

bte et v'iretion, under the entier or extern ei rares, in contri-ct with siii iip, u carried by seid block7 :irl sind strip holding; m.

phi-iugm Ad .in contect i i ot seid dmpiree/mi ndo nel studs arranged i i i outside of endl tint tue o iuphre @in ite secured 'over but si trom seid dieL 'zi-rm :nid :Wing sound inlets therein oppositie the fibrutory portions et the diaphragm, sei/1 ,r1-'i n' ineens und studs and pressing tiese parts inwei l2. A teieehone treismitt compi insiuutiiig materiel h Y( dieiuetriceiiy erinie'ec. recesses therein, eiee 'trodes arenpjed in uuid s ne' ii( the ieee of seid bioek'and between end over seid electrodes and tiroutjwhich eiectrie cover plete being errzineld recesses, ifi/loyer or grunu...zir conducting nie-te` il extending` over Current can flow, a sound sensitive diaphragm torred ot thin iionmesonant noneoondueting material forming slrin touching the layer of granular material, rings between which and the eripheral portion of said bloolr the peripheral portion of said diaphragm is clamped, a second ring secured a diametrieal strip of material arranged opposite to and bearing against a diametrical portion oi said diaphragm at right angles to a diainetrical line passing through said electrodes, and a plate adapted to press said rings and periph? eral portion oit the diaphragm against said bloclrand the diametrioal strip against the diaphragm and having openings therein opposte the portions ot diaphragm between,

the Clamping rings and strip. y

13. A telephonie transmitter comprising a circular block ot insulating material having oppositely arranged lateral are shaped reeesses therein, electrodes .having irregular up-l per surfaces secured in said recesses, a layerV of granular oondiwI g material extending over the tace of said bloclr and between an l' over the. upper surfaces of said electrodes, a ring of insulating material extending around the electrodes and forming with said block a receptacle for the layer oiE Conducting material., a second ring arranged above the first mentioned one, a sound sensitive diaphragm extending over the layer o'i conducting maerial and electrodes and having its peripheral portion clamped between said rings, a third ring bearing at its periphery against the seo-` ond ring and .having a diainetrieall'y arranged portion, and a strip of material arrangedv between suoli diametrioally arranged portion or said third ring and a diametrioal portion oil said diaphragm-and bearing firmly against the latter in a. direction at right angles to a diametrieal line passing through the electrodes, said third ring having sound inlet apertures therein opposite the unclamped lateral portions of said diaphragm at each side oi the diainetrieall;7 held portion ot the dia phragm.

lil. The combination vith la telephone transmitter according to claim 1.3, oi? a casand an inwardly ilanged cap ring secured to said casing ano adapted to press the third rng an d clamping rings with interposed pel g i plier-al portion of the diaphragm against d bloolr and the diametrical strip oi maagainst said diaphragm. A telephone transini ter comprising a circular bloelr et insulating material, op-l oositeiy and laterally arranged segmental shaped electrodes lixed in said block a la er of granular conducting material extending over the i'ace oi said block and between andy over said electrodes, a ring of insulating material surroundin@ said electrodes and forming with the face of said bloelna receptacle for the conduct-ing material, a second ring arranged adjaeent to the first one, a diaphragm formed oi' thin sheet rubber clamped at its periplier'r7 between said rings, a plate arranged adjacent to the second ring' and provided with a dia-metrica ly arranged member andA with sound inlet apertures at opposite sides of said member said rings and plate being secured to said bloelna diametrieally arranged strip of ieiding material arranged between the diametrieal member of said plate and said diaphragin'and bearing iirmly against a diametrioal portion of said diaphragm, two strips of relatively soit. insulating material arranged adjacent to said electrodes and parallel to said diametrically arranged strip ot yielding material and eaoh provided with a series oi' studs bearing against the inner side of said diaphragm, and two diametrioally arranged studs arranged between the said plate and diaphragm and acting to press said dia phragm against the layer ot conducting materiah 16. A telephone transmitter comprising a circular bloclr of insulating material having diainetrieallj,7 arranged recesses therein, electrodes arranged-in said recesses, a layer of granular conducting material extending over the face ot said bloelr and between and incontaot with said electrodes, a circular sound sensitive diaphragm formed of thin non-resonant non-conducting material forming a skin 'touching the layer oifeonductingmaterial and extending over the peripheral end portion oit said bloolna ring bearing against the peripheral portion oi' 'said diaphragm, a strip of material arranged to bear against a diametrical portion of said diaphiagm.v at right angles vto a diametrioal line passing through said electrodes, so as to leave portions oi' the diaphragm between said ring and strip free to vibrate independently of eaeh other and a plate radapted to press said ring and strip against said diaphragm land having openings therein opposite the portions of the diaphragm that are tree to vibrate.

Signed at l t Graceehureh Street, in the city oi London, this twenty-sixth day oi' May,

MARA GRAHAM, Eeoutrim v0,1 Edward Alf/feel Groifmi, De-

ceased.

'ALFRED GRAHAM, Eazeoator of Edit/*ard Alfred Graham, De-

ceased.

LE SLIE HAROLD PADDLE.

llO 

